More than 60 years after the end of World War II, an 89-year-old retired auto worker from Ohio went on trial in Germany on Monday in what many are calling the country's last Nazi war-crimes proceeding. That's not the only reason the world is watching the trial closely: John Demjanjuk is also No. 1 on the Simon Wiesenthal Center's list of most wanted war criminals, accused of being an accessory to the deaths of at least 27,900 people. Then there's the added drama of his health  Demjanjuk's family insists he's too old and sick to stand trial, claiming he's suffering from a range of ailments. He was pushed into the courtroom in a wheelchair on Monday morning, his mouth slightly agape and apparently struggling for breath. During the afternoon hearing, he was brought in lying on a gurney. When he started writhing and complaining of pain, he was taken outside for an injection.

Prosecutors say that Demjanjuk, who was born in Ukraine and emigrated to the U.S. in 1952, worked as a guard at the Sobibor extermination camp in Nazi-occupied Poland in 1943 and that his job was to lead thousands of Jews to their deaths in the gas chambers. Demjanjuk fought for the Russians first, however. According to prosecutors, he was taken prisoner by the Germans in 1942 and then sent for training to become a Nazi guard at a special camp in eastern Poland called Trawniki, which was run by Adolf Hitler's élite SS force. Crucial to the prosecution's case is an ID card from Trawniki purportedly showing that Demjanjuk was transferred from the SS training camp to Sobibor in March 1943. (See pictures of the rise of Adolf Hitler.)

The prosecutors' charge sheet carries a detailed description of Demjanjuk's alleged duties at Sobibor. "When the transport train carrying Jews arrived, the normal work was stopped and each member of the camp personnel became involved in the routine extermination process," the document reads. After the Jews were ordered out of the cars, they were told to leave their luggage on the ramps and take off their clothes, the charge sheet says. They were then allegedly led to the gas chambers under the pretext they were taking a shower. Holocaust experts have also linked the Sobibor guards to mass executions. "The guards were involved in the extermination process  the Nazis had few personnel in the death camps and the people who were there played an integral part in genocide," Dr. Edith Raim, a historian at Munich's Institute of Contemporary History, tells TIME.

More than 30 plaintiffs, including former Sobibor inmates and relatives of those killed, are attending the trial in Munich. Nineteen will give evidence in the case. But it's unlikely that anyone will be able to identify Demjanjuk after 66 years  one of the main obstacles that prosecutors face. There are no living witnesses who can tie him to specific killings, so prosecutors will have to rely on past statements from witnesses who are now deceased and written documents. If convicted, Demjanjuk faces up to 15 years in prison  the usual maximum sentence in Germany. (See pictures of the faces of D-Day.)

Survivor Thomas Blatt, whose brother and parents died at the camp, has traveled from his home in California to Germany to testify. But even he admits it will be difficult to convict Demjanjuk. "I can't remember the faces of my parents now," the 82-year-old says. "How could I remember him?" Blatt says the trial is important, nonetheless. "I don't care if he ends up in prison or not," he says. "The world needs to find out what happened at Sobibor."

Demjanjuk has a different take on the past. He portrays himself as a victim of the Nazis  a Red Army conscript who was captured by the Germans and then held as a prisoner of war in different camps. Demjanjuk has thus far remained silent about the charges leveled against him. "I expect he won't say anything during the whole trial," says his lawyer, Günther Maull. And, he adds, even if prosecutors can prove that Demjanjuk was at Sobibor, Maull maintains that he would have been there under duress. (Read "New Trial for Nazi War-Crimes Suspect?")

After gaining U.S. citizenship in 1958, Demjanjuk lived an unassuming life with his family in Cleveland, Ohio, working at a Ford car factory until evidence surfaced suggesting he had been an SS guard at the Treblinka death camp in Poland. The U.S. government revoked his citizenship and, in 1987, Demjanjuk went on trial in Israel, accused of being the notorious guard Ivan the Terrible. He was convicted of crimes against humanity and sentenced to death. But in 1993, his conviction was overturned on appeal by the Israeli Supreme Court, which ruled that he wasn't the guard in question. Demjanjuk returned to the U.S., but German authorities soon requested his extradition. Demjanjuk's family argued he was too ill to travel, but they lost their legal battle and he was finally deported to Germany in May. (Read a 2-Min. Bio of Demjanjuk.)

Doctors who examined Demjanjuk testified on Monday that while he's frail, he's fit to stand trial and he's not suffering from dementia. The hearings will be limited to two 90-minute sessions each day so as not to tire him out. If his health deteriorates further, however, there's a chance the whole trial may grind to a standstill. As for the survivors and the relatives of those killed at Sobibor, they're just relieved the trial has started.